The present invention relates to a distance sensor device, and in particular, relates to use of a distance sensor device as a component of a parking aid or reversing aid for a motor vehicle, having one or more distance sensors and a distance sensor control device for activating the one or more distance sensors by way of a respective signal line by means of an activation pulse that is preferably quasi-digital and time-analog.
Parking and reversing aids can be used as accessories for motor vehicles. These products may include several (up to ten) ultrasonic sensors, a control device assigned thereto, and one or more acoustic or optoacoustic warning elements for the driver.
FIG. 5 illustrates a conventional ultrasonic distance sensor device for a reversing aid having four ultrasonic sensors US and a control device US-SG. Four signal lines as well as a power supply line and a ground line run from control device US-SG to a distributor V. From distributor V, one signal line as well as the power supply line and ground line run to each ultrasonic sensor US.
The activation of ultrasonic sensors US by way of the respective signal line occurs by way of a respective bidirectional open collector interface. With respect to amplitude, the transmission occurs in a quasi-digital, but time-analog manner.
FIG. 6 shows an activation pulse produced internally in the control device for an ultrasonic sensor US of the device according to FIG. 5. Time t is plotted on the x axis and voltage amplitude U is plotted on the y axis.
The duration of this activation pulse, which activates the measuring procedure in ultrasonic sensor US, is t1-t0 (typically 300 xcexcs). Thus, at the beginning of time t0, ultrasonic sensor US begins to transmit its ultrasonic pulse.
FIG. 7 shows the signal response produced internally in ultrasonic sensor US for an ultrasonic sensor US of the device according to FIG. 5. Time t is plotted on the x axis and voltage amplitude U is plotted on the y axis.
A comparator, which is not shown, inspects or monitors the signal voltage of the ultrasonic transducer for a sufficiently high received amplitude, and the voltage is only assessed as the detection of an object above a certain minimum amplitude, in order to eliminate sound effects or interference effects.
The time interval between t2 and t3 shows the mechanical vibration of the sensor membrane as a result of the activation. The time between t4 and t5 has the detected ultrasonic energy that has been reflected by an object.
FIG. 8 shows the signals on the data line between control device US-SG and ultrasonic sensor US as a whole for the known ultrasonic distance sensor device according to FIG. 5. Time t is plotted on the x axis and voltage amplitude U is plotted on the y axis.
The time difference between t0 and t4 represents distance s between the reflecting object and ultrasonic sensor US that is calculated in control device US-SG. The following formulas shall apply:
S=Cs*te/2xe2x80x83xe2x80x83(1)
and
te=t4xe2x88x92t0xe2x80x83xe2x80x83(2)
where cs is the speed of sound in air.
Unfortunately, the measuring range of the ultrasonic sensors currently available on the market is limited to approximately 2 m.
The exemplary embodiment of the present invention involves the creating a more flexible distance sensor device.
It is believed that the distance sensor device according to the present invention has the advantage that it is compatible with a conventional ultrasonic sensor in its function and interface and creates the corresponding request-specific function control for an extended functionality by way of the exemplary transmitting/receiving line using the exemplary control device.
It is believed that the similarity in function and interface between the microwave sensor and conventional ultrasonic sensors provides the advantage that an exemplary control device and exemplary software may be used in the same manner with microwave sensors for its current functionality.
It is also believed that the distance sensor device according to the present invention provides additional advantages including the possibility of mixing sensors having various physical properties or sensing principles and the possible structural similarity of the microwave sensor for various applications having different requirements regarding their numbers.
It is also believed that using an exemplary control device, the measuring range and type of measurement for the requirements of different functionalities may be changed.
It is also believed that the measurement values may be filtered using a microcontroller in the exemplary sensor, as well as a self-diagnosis of the exemplary control device and a remote diagnosis of the sensors.
According to the an exemplary embodiment of the present invention, at least one of the exemplary distance sensors has two different modes of operation and may be switched between modes of operation by varying the duration and/or amplitude of the activation pulse of the distance sensor control device.
According to another exemplary embodiment, the distance sensors have several ultrasonic sensors and several microwave sensors. According to one implementation, the ultrasonic sensors have one mode of operation and the microwave sensors have several modes of operation, microwave sensors being particularly suitable for switching between modes. Thus, a microwave sensor may therefore be implemented with a functionally compatible ultrasonic sensor interface and the ability to switch for various requirements. In this manner, the requirements for, e.g., faster measurement cycles, greater ranges, monitoring of a distance section, calculation of the relative speed, data transmission, or strong EMC irradiation (EMC=electromagnetic compatibility) may be switched via the control device. It is believed that an exemplary interface for emulating an ultrasonic sensor may then remain unchanged for the purposes of hardware.
According to another exemplary embodiment, a bidirectional open collector interface is provided between the distance sensor control device and the respective distance sensor.
According to another exemplary embodiment, the various modes of operation may include one or more of measuring range modes, signal transmission modes, test modes, and service modes for the purpose of adjusting or calibrating the sensor.
According to another exemplary embodiment, the modes of operation may include a digital signal transmission mode. It is believed that a switching of an exemplary time-analog, possibly quasi-digital interface into a bidirectional, digital interface with a fixed data format and established protocol may be implemented by using an activation pulse from the control device. It is also believed that it is advantageous in that the exemplary data transmission interface having the exemplary sensor allows lower transmission rates.
According to another exemplary embodiment, the exemplary distance sensor control device is a common control device for all distance sensors that is connected to each distance sensor by way of a single signal line. It is believed that a conventional ultrasonic sensor control device may therefore be used for the functionality that has been extended according to the present invention.